Preparation of cyclopentadiene metal compounds



B,G8,960 PREPARATION OF CYCLOPENTADIENE METAL CQMPOUNDS John C.Wollensak, Royal Oak, MiclL, assignor to Ethyl Corporation, New York,N.Y., a corporation of Delaware N Drawing. Filed Aug. 20, 1959, Ser. No.834,928 13 Claims. (Cl. 260-439) This invention relates to a new andimproved process for the preparation of organometallic compounds. Morespecifically this invention relates to a process for formingorganometallic compounds in which a bis(cyclopentadienyl) metal compoundis reduced to form a compound in which one or more cyclopentadienemolecules are bonded to the metal atom.

An object of this invention is to provide a process for [formingorganometallic compounds. A further object is to provide a new processin which a bis(cyclopentadienyl) metal compound is reacted with ared-uctant to form compounds in which one or more cyclopentadienemolecules are bonded to the metal atom. A more specific object is toprovide a process in which are produced organometallic compounds of themetals selected from the group consisting of cobalt, rhodium, iridium,and nickel having one or more cyclopentadiene molecules coordinated withthe metal atom. Further objects will become apparent by a reading of thespecification and claims which follow.

The invention involves formation of organometall'ic compounds in whichone or more cyclopentadiene molecules are coordinated with the metalatom, by reacting a bis(cyclopentadienyl) compound of a metal selectedfrom the group consisting of cobalt, rhodium, iridium and nickel with areducing agent. When the starting material is a bis(cyclopentadienyl)metal compound of cobalt, rhodium, or iridium, the resulting product isa compound in which both a cyclopentadienyl radical and acyclopentadiene molecule are coordinated with the metal atom. When thestarting material is a bis(cyclopentadienyl) compound of nickel, theproduct is a bis(cyclopentadiene) nickel compound.

The compounds produced by our process are electronically neutral,reasonably stable compounds. This is so because the central metal atompresent in the compounds has attained the configuration of the nexthigher rare gas above it in the periodic table by virtue of the donatedelectrons from the cyclopentadienyl radical and cyclopentadienemolecule. To illustrate, the compound cyclopentadienyl cobaltcyclopentadiene produced by our process has the following structuralconfiguration:

v ice As shown, two cyclopentadiene molecules are coordinated with thenickel atom. Each cyclopentadiene molecule donates four electrons to thenickel atom for bonding, thereby giving it the electronic configurationof krypton which is the next higher rare gas above nickel in theperiodic table. I

1 am not bound 'by any theory regarding the nature of my process.However, in order to explain the fact that my process producescyclopentadienyl metal cyclopentadiene compounds of cobalt, rhodium, andiridium and conversely produces bis(cyclopentadiene) compounds ofnickel, it is assumed that the metal atoms have a driving force towardattainment of rare gas configuration. Reduction of a singlecyclopentadienyl radical leads to rare gas configuration when thestarting material is a bis(cyclopen-tadienyl) metal compound of cobalt,rhodium, and iridium. Thus, the reduction stops at this point. On theother hand it is necessary that both cyclopentadienyl radicals bereduced when the starting material is a bis- (cyclopentadienyl) nickelcompound in order that the nickel atom attains rare gas configuration.Therefore, reduction in this case does not stop until bothcyclopentadienyl radicals have been reduced.

My process involves the reduction of a compound having the formula Cy M.M in the above formula is a metal selected from the group consisting ofcobalt, rhodium, iridium and nickel. Cy represents a cyclopentadienylradical which may be substituted with various substituents andpreferably contains from 5 to about 13 carbon atoms. Typical of thesubstituents which may be present on the cyclopentadienyl radical arealkyl groups such as methyl, ethyl, propyl, n-butyl, tert-butyl, hexyland the like. The substituent groups may be aryl groups such as benzyl,pmethyl phenyl, and the like. Also, the substituent groups may thecycloaliphatic such as cyclohexyl, cyclopentyl; alkenyl groups such aspropenyl, .butenyl, pentenyl and the like, and cycloalkenyl radicalssuch as cyclohexenyl, cyclopentenyl and the like. In addition thecyclopentadienyl radical may be substituted with groups containinghetero atoms such as halogens, amines and the like. Typical of suchgroups are trichloromethyl, fluoro, dimethylamino, dihexylamino and thelike.

Typical of the bis(cyclopentadienyl) metal compounds utilized asreactants in our process are bis(cyclopentadienyl) cobalt,bis(cyclopentadienyl) nickel, bis(methylcyclopentadienyl) rhodium,bis(propylcyclopentadienyl) iridium, bis(diethylcyclopentadienyl)nickel, bis(phenylcyclopentadienyl) cobalt,bis(trichloromethylcyclopentadienyl) nickel,bis(dimethylaminocyclopentadienyl) cobalt,bis(p-chlorobenxylcyclopentadienyl) nickel, and the like. When reducedaccording to my process these compounds yield respectivelycyclopentadienyl cobalt cyclopentadiene, bis(cyclopentadiene) nickel,methylcyclopentadienyl rhodium methylcyclopentadiene,propylcyclopentadienyl iridium propylcyclopentadiene,bis(diethylcyclopentadiene) nickel, phenylcyclopentadienyl cobaltphenylcyclopentadiene, bis(trichloromethylcyclopentadiene) nickel,dimethylaminocyclopentadienyl cobalt dimethylaminocyclopentadiene andbis(p-chlorobenxylcyclopentadiene) nickel.

My process takes the form of several embodiments. The first embodimentinvolves the reaction of a bis(cyclopentadienyl) metal compound asdefined above with an alkali metal amalgam in the presence of ahydrolytic solvent. A preferred form of this embodiment involves thepreparation of compounds as defined above in which the: cyclopentadienemoiety is substituted only with hydrogen or a hydrocarbon substituent.The alkali metal amalgam may comprise, for example, sodium, lithium, orpotassium amalgamated with mercury. The solvent is hydrolytic; that is,it contains a replaceable hydrogen atom. In this. embodiment it isessential that the solvent contain a replaceable hydrogen atom since inthe reduction of the bis- (cyclopentadienyl) compound a source ofhydrogen is re quired to convert the cyclopentadienyl radical tocyclopentadiene. Typical of such hydrolytic solvents are the: alcohols.Preferably, the alcohol solvent contains from one to four carbon atoms.Examples of such alcohols are methyl alcohol, ethyl alcohol, propylalcohol and butyl alcohol.

The process embodiment defined above involving the; use of an alkalimetal amalgam in the presence of a hydrolytic solvent is preferred toother of my process embodiments as defined later. This embodiment ispreferred since it gives in general better yields of product with less.occurrence of undesirable side reactions than do the other embodiments.

In conducting my process according to the first process embodiment, thetemperature employed may range be tween about --20 C. to about 100 C.Preferably the temperature is maintained between about zero to about 35C. during the reaction, since within this range good yields of productare obtained with a minimum of undesirable side reactions occurring. Thepressure employed is not critical and pressures up to 100 atmospheres ofinert gas can be used. Preferably, however, the pressure is maintainedbetween about atmospheric pressure and about 'five atmospheres. Aprotective atmosphere is preferably employed in the reaction vesselsince this prevents decomposition of the reactants or products. Typicalof the inert gases which may be used as a protective atmosphere arenitrogen, argon, helium, krypton, and neon. The reaction mixture is.preferably agitated so that the reactants are intimately dispersed. Thisis extremely desirable since without agitation the reactants cannotcontact each othersufiiciently to maintain an even reaction rate.

In general the time required for the reaction varies between about 30minutes and about 12 hours. The time requirement is not critical,however, since the time required will vary with the reaction temperatureand the quantities of reactants used. Thus, if the reaction temperatureis high and certain of the reactants are used in excess, the reactiontime will be relatively short. Conversely, if a low temperature isemployed and the reactants are used in stoichiometric quantities, thereaction time will be longer.

In general, an excess of alkali metal amalgam is utilized in theprocess. For each mole of bis(cyclopentadienyl) metal reactant, thereare preferably employed from about three to about six moles of alkalimetal as amalgam.

'Greater or lesser quantities of alkali metal amalgam can be employedalthough in general this decreases the elficiency of the process;

'The composition of the alkali metal amalgam generally comprises betweenabout two to about 5 percent by weight of alkali metal. Greater orlesser quantities of alkali metal can be employed in the amalgam but theuse of such quantities may reduce the effectiveness of the reaction. Forexample, if the concentration of alkali metal is less than two percent,the reaction rate may be decreased because of the decreased contactbetween the alkali metal and the bis(cyclopentadienyl) reactant. Whenthe alkali metal content in the amalgam is higher than five percent,some alkali metal may be present in unamalgamated form. At suchconcentrations the alkali metal may, in a free form, react withexplosive violence if water is present in the system. This result isundesirable since in some instances water is employed in the process.

As stated above, the preferred solvent for use in the process is analcohol containing from about one to about four carbon atoms. Suchalcohols are hydrolytic and supply hydrogen for the reacton. Othersolvents may be employed, however. For example, a mixed solventcomprising up to about 10 percent by weight of water admixed withalcohol can be employed. A mixed solvent can be employed containing upto about 10 percent by weight of water admixed with a highly polar ethersuch as tetrahydrofu-ran, ethylene glycol dimethylether, ethylene glycoldiethylether, ethylene glycol dibutylether, diethylene glycoldimethylether, diethylene glycol diethylether, diethylene glycoldibutylether, and the like.

Other mixed solvents which can be employed are those comprising 10percent or more by weight of an alcohol containing from about one toabout four carbon atoms and a neutralhydrocarbon or ether solvent.Typical of the solvents with which the alcohol can be admixed are thealiphatic hydrocarbons such as n-hexane, n-octane, isooctane, n-heptane,various isomers of hexane, octane and heptane, or mixtures of the above.Other suitable neutral solvents are the cycloaliphatic hydrocarbons suchas cyclo hexane or methylcyclohexane. Straight and branched chainolefins such as isoheptene, n-hexene, isooctene, and n-octene are alsoapplicable. Aromatic hydrocarbon sol vents such as benzene, toluene,ethylbenzene and Xylene, either mixed or pure, may also be used.

Other solvents which can be employed are mixtures comprising 10 percentor more by weight of an alcohol, as defined above, admixed with an ethersolvent. Typical of such ether solvents are the cyclic ethers such astetrahydrofuran, and 1,3-dioxane. Non-cyclic monoethers such asdiethylether, diisopropylether and diphenylether are also applicable.Other ethers which may be admixed with an alcohol are ethylene glycoldimethylether, ethylene glycol diethylether, diethyleneglycoldimethylether, diethylene glycol diethylether, and the like.

The amount of solvent used in the process is not critical. Generally,however, sufficient solvent is employed to dissolve thedicyclopentadienyl metal reactant. Use of less solvent than this amountis permissible so long as a fluid reaction mass is maintained. Use of agreat excess of solvent does not unduly hinder the process but its usegenerally achieves no purpose. Also, the use of a large excess ofsolvent dilutes the reaction mass and thereby diminishes the reactionrate; extra process equipment is required to handle increased solventthroughput, and more valuable solvent is lost through evaporation,leakage, etc.

The other process embodiments involve use of a reductant other than analkali metal amalgam. A second process embodiment involves the use of asimple or complex alkali metal hydride as the reductant. Examples ofsuch hydrides are sodium borohydride, lithium aluminum hydride, lithiumborohydride, potassium borohydride, magnesium bis(aluminum hydride),sodium trimethoxy borohydride, sodium hydride, lithium hydride, cesiumhydride, rubidium hydride, potassium hydride and the like. The complexalkali metal borohydrides are preferred hydrides for reducingbis(cyclopentadienyl) metal compounds, as defined above, in which thecyclopentadienyl moiety contains hetero substituents that are easilyreduced. The borohydrides are milder reducing agents than other alkalimetal hydrides. Their use thereby enables reduction of thebis(cyclopentadienyl)metal compound without reducing the heterosubstituents.

When using a simple or complex alkali metal hydride as the reductant,the same solvents may be employed as previously set forth for the alkalimetal amalgam embodiment. Certain alkali metal hydrides are extremelyreactive, however, and in some cases it is not desirable to use water ina weight concentration up to percent of the solvent mixture. Forexample, when using sodium hydride as the reductant, I prefer tomaintain the water concentration at less than two percent by weight.Selection of a solvent that is not too reactive with the alkali metalreductant is within the skill of the art when practicing my process. Inmy process, therefore, the water concentration can be adjusted to suitthe reactivity of the alkali metal reductant.

The temperature at which reaction may be carried out when using analkali metal hydride ranges from about zero to about 100 C. Preferredtemperatures are about zero to about 50 C. since within this rangeyields are maximized and undesirable side reactions are minimized. Theprocess is preferably carried out under an inert atmosphere of, forexample, nitrogen, argon, krypton or neon. Agitation is preferablyemployed in the process since it insures intimate contacting of thereactants and a steady reaction rate. The process pressures are notcritical and up to 100 atmospheres of inert gas pressure can be used.Preferably pressures ranging from about one to about five atmospheresare employed.

From about one to about six moles of alkali metal hydride are generallyemployed for each mole of bis(cyclopentadienyl)metal compound. Greateror lesser quantities of alkali metal hydride can be used but in generalthe reaction works best within the above specified range. The amount ofsolvent employed is not critical but in general sufficient solvent isemployed to dissolve the cyclopentadienyl metal reactant. Use of a largeexcess of solvent does not greatly hinder the reaction but in general isavoided. It may result in solvent loss and a slower reaction rate due todecreased contact between the reactants.

Another embodiment of my process involves the use of an alkali metal asthe reductant. In using an alkali metal as reductant, a preferred formof my process involves reduction of a bis(cyclopentadienyl)metalcompound in which the cyclopentadienyl moieties are substituted onlywith hydrogen or a hydrocarbon substituent. This embodiment is closelyrelated to the previous embodiment utilizing an alkali metal hydridereductant. In general, the same conditions apply to this embodiment asapply to reduction via an alkali metal hydride. Since the alkali metals,e.g., sodium, potassium, lithium, cesium, and rubidium are somewhat morereactive than the alkali metal hydrides, precautions must be taken as tothe composition of the solvent employed. The alkali metals reactvigorously with water and relatively high concentrations of water in thesolvent should therefore be avoided. Water concentration in the solventwhen using an alkali metal reductant should generally not exceed onepercent by weight. Higher concentrations can be used but their use maymake the reaction rate hard to control. In many cases, it is, therefore,desirable to dilute the solvent containing water or an alcohol aspreviously defined, with additional inert solvent. Since many of thealkali metals react rapidly with alcohols, high alcohol concentrationsshould be avoided since they will make the reaction diflicult tocontrol. Use of higher alcohols, e.g., butyl or propyl, is frequentlyadvantageous in the process since higher alcohols are less reactive withrespect to the alkali metal. They can be employed with less risk ofletting the reaction rate get out of hand.

A further process embodiment differing slightly from previousembodiments involves the reaction of a cyclopentadienyl metal compoundas previously defined with hydrogen in the presence of a neutral solventand a hydrogenation catalyst. Typical hydrogenation catalysts such asRaney nickel, platinum, palladium, and copper chromite can be used. Thecatalyst is generally employed in a small amount ranging up to a maximumconcentration of about 30 percent by weight of thebis(cyclopentadienyl)metal compound to be reduced. Ordinarily, excesshydrogen is employed. Use of excess hydrogen tends to force the reactionto completion and thereby results in higher product yields in a shortertime period. in order to insure an excess of hydrogen, the reaction ispreferably conducted under at least about one atmosphere of hydrogenpressure. Higher pressures up to about five atmospheres of hydrogen canbe employed but in general pressures in the order of one atmosphere arepreferred. Excess hydrogen which is not consumed in the reaction can bereadily recovered and recycled to the reaction vessel. In this processembodiment a preferred species is the reduction of abis(cyclopentadienyl) metal compound in which the cyclopentadienylmoieties are substituted only with hydrogen or a hydrocarbonsubstituent.

During the process the reaction mixture is preferably agitated. Thisresults in intimate contacting of reactants and a smooth and evenreaction rate. Process temperatures can range from between about zero toabout C. Preferably the temperature ranges between about 25 to about 50C. Within this latter range maximum yields of product are obtained witha minimum of undesirable side reactions. The pressure is not criticaland may range between about one to about atmospheres of an inert gas.Higher pressures may be used although this is generally notadvantageous.

Unlike preceding process embodiments this embodiment does not require asolvent which is hydrolytic. Hydrogen is added directly to the reactionmixture and it is, therefore, not necessary that the solvent containactive hydrogen. Hydrolytic solvents may be employed however withoutadversely affecting the reaction. Typical of the solvents which may beemployed are aliphatic hydrocarbons such as hexane, heptane, n-octane,n-nonane and isomeric forms of the preceding hydrocarbons. Alsocycloaliphatic hydrocarbons are applicable such as cyclohexane, methylcyclohexane and the like. Aromatic solvents such as toluene, benzene andxylenes either pure or mixed, can be used.

Ether solvents such as ethyl octylether, ethyl hexylether, diethyleneglycol diethylether, diethylene glycol dimethylether, diethylene glycoldibutylether, ethylene glycol dimethylether, ethylene glycoldiethylether, ethylene glycol dibutylether, dioxane and the like aresuitable. Silicone oils such as the dimethyl polysiloxanes, methylphenyl polysiloxanes, di-(chlorophenyl)polysiloxanes, hexapropyldisilane and diethyldipropyldiphenyldisilane may also be employed.Included also are pentyl butanoate, ethyl decanoate, ethyl hexanoate andester solvents derived from poly acids such as succinic, malonic,glutaric, adipic, pimelic, suberic, azelaic, sebacic and pinic acids.Specific examples of the diesters are di-(r2-ethylhexyl) adipate,di-(Z-ethylhexyl) azelate, di-(Z-ethylhexyl) sebacate, di-(methylcyclohexyl) adipate and the like. Also applicable, as previously stated,are hydrolytic solvents as defined previously. Such solvents include thealcohols, e.g., methyl, ethyl, propyl and butyl alcohol,

water admixed with one of the foregoing alcohols, or a mixture of waterand/ or an alcohol with an inert organic solvent.

To further illustrate our process, there are presented the followingexamples in which all parts and percentages are by weight unlessotherwise indicated.

Example 1 A mixture of 3.2 parts of nickelocene and 38.6 parts of a fivepercent sodium amalgam in 79 parts of absolute ethanol was stirred at 0C. under nitrogen atmosphere for 2.5 hours. During the reaction period,the nickelocene reacted to give a red-brown reaction mixture. Theethanol suspension was decanted from the mercury into a separatoryfunnel and about 200 parts of water and about 64 parts of petroleumether were added. The ortaining finely divided alumina.

ganic phase was washed twice With water and dried rapidly over magnesiumsulfate at a reduced temperature. It was then concentrated by heating invacuo to dryness to give 2:12 parts of a red-crystalline residue. Theresidue was recrystallized from petroleum ether at 78 C. to give 0.6part of bis(cyclopentadiene) nickel having a melting point of 38-42" C.Sublimation of this product at room temperature and 0.2 mm. pressuregave an analytical sample of bis(cyclopentadiene) nickel having amelting point of 43-44.5 C. Analysis.Calculated for C H Ni: C, 62.91; H,6.31; Ni, 30.75. Found: C, 63.0; H, 6.52; Ni, 30.5. The mother liquorsof the crystallization were sublimed and yielded an additional 0.95 partof semi-pure bis(cyclopentadiene) nickel having a melting point of -43C. The compound is sensitive to air and decomposes under nitrogen at 175C. The compound is diamagnetic and its structure was further supportedby infrared analysis.

Example 2 A mixture comprising 3.1 parts of freshly sublimedcobaltocene, 57.6 parts of 5 percent sodium amalgam and 79 parts ofabsolute alcohol were stirred at 0 C. for three hours under a nitrogenatmosphere. During the reaction period, the sodium amalgam reactedcompletely and the color of the mixture changed from purple to redbrown.The solvent was removed at 20 mm. pressure and room temperature to givea red semi-solid mixed with mercury metal. This mixture was subjected tosublimation at 75 C. and 20 mm. causing the separation of 1.05 parts ofcrude cyclopentadienyl cobalt cyclopentadiene as long, dark-red needleshaving a melting point of 107- 115 C. The product was further purifiedby chromatographing through a column packed with alumina and elut ingwith petroleum ether. A brick-red band, which separated first, wasconcentrated to a red crystalline solid. Sublimation of the solid at 90C. and 20 mm. gave 0.46 part of red crystals (cyclopentadienyl cobaltcyclopentadiene) having a melting point of 94-95 C. The structure of theproduct was further confirmed by infrared analysis.

Example 3 A mixture of 6.32 parts of nickelocene and about 2.5 parts ofRaney nickel in 197 parts of absolute ethanol was stirred and treatedwith hydrogen at atmospheric pressure and room temperature. Whenslightly more than two equivalents of hydrogen were taken up, thehydrogenation was stopped and the reaction product was discharged. Thereaction product was then filtered and concentrated to dryness. Theresidues were chromatographed through an alumina-packed column. Theproduct was eluted with petroleum ether. Two bands, one green and onered, were observed. The red band was separated and dried to give 0.2part of bis(cyclopentadiene)nickel. The green band, when separated anddried, gave 0.8 part of unreacted nickelocene.

Example 4 To a stirred solution comprising 1.88 parts of nickelocene in19.7 parts of absolute ethanol under a nitrogen atmosphere were added0.37 part of sodium borohydride. The sodium borohydride was added all atonce. On warming the reaction vessel in a water bath for a few minutesat 50. C. an exothermic reaction was initiated. The reaction mixturerapidly turned black and hydrogen gas was evolved. After about 15minutes, vigorous reaction had ceased and the mixture was stirred atroom temperature for an additional minutes. Two hundred parts of waterand 158 parts of ethylether were added to give two phases whichcontained a black suspension. The mixture was filtered and the phaseswere separated. The ether phase was washed with Water, dried overmagnesium sulfate and concentrated in vacuo to a green-brown partiallycrystalline mass. This was placed in a column con- Elution withpetroleum ether gave first an orange band which on concentration gave ared semi-solid. Crystallization of the solid from petroleum ether gave0.1 part of bis(cyclopentadiene) nickel as dark red prisms. Theirmelting point was 38 40 C. A second band, eluted with petroleum ether,was nickelocene. When concentrated and recrystallized from petroleumether the nickelocene gave dark green crystals having a melting point of166170 C. with decomposition.

Example 5 One mole of bis(methylcyclopentadienyl) nickel is dissolved inbutyl alcohol and six moles of potassium as a two percent potassiumamalgam are charged to an evacuated autoclave. The autoclave ispressurized to five atmosphotos with argon. The mixture is heated withstirring for 30 minutes at 35 C. after which the autoclave is cooled andthe contents are discharged. The product, bis(methylcyclopentadiene)nickel is separated from the solvent by means of chromatography. A goodyield is obtained.

Example 6 Two moles of bis(octylcyclopentadienyl) rhodium dissolved in asolvent comprising 10 percent water and percent tetrahydrofuran ischarged to an autoclave along with three moles of lithium in the form ofa three percent lithium amalgam. The autoclave is pressurized withhelium to atmospheres. The autoclave is cooled to 20 and maintained atthis temperature for 12 hours while the reaction mixture is stirred. Itis then vented and the product is discharged. A good yield ofoctylcyclopentadienyl rhodium octylcyclopentadiene is obtained by separation of the product from the solvent through chromatography.

Example 7 One mole of bis(methylcyclopentadienyl) cobalt dissolved in asolvent comprising 50 percent propyl alcohol and 50 percent benzene ischarged to an evacuated autoclave along with one mole of lithiumaluminum hydride. The vessel is pressurized to one atmosphere ofnitrogen. The reaction mixture is stirred for three hours at 0 C.whereupon the autoclave is discharged. The productmethylcyclopentadienyl cobalt methylcyclopentadiene is recovered in goodyield from the solvent by chromatography.

Example 8 Two moles of bis(trichloromethylcyclopentadienyl) nickeldissolved in methyl alcohol is charged to an evacuated autoclave alongwith two moles of sodium borohydride. The vessel is pressurized withnitrogen to one atmosphere. The mixture is stirred for two hours at 20C. and the vessel is discharged. The productbis(trichloromethylcyclopentadiene) nickel is recovered in good yield bychromatography.

Example 9 One mole of bis(cyclopentadienyl) iridium dissolved in asolvent comprising two percent water and 98 percent dioxane is chargedto an evacuated autoclave along with six moles of sodium hydride. Theautoclave is pressurized to 1-00 atmospheres with argon and stirred for30 minutes at 30 C. The vessel is then discharged and water is added tothe reaction mixture. The mixture is filtered and the solids aredissolved in petroleum ether. A good yield of cyclopentadienyl iridiumcyclopentadiene is recovered from the ether by means of fractionalcrystallization.

Example 10 One mole of bis(dimethylcyclopentadienyl) nickel dissolved inabsolute ethanol is charged to an evacuated autoclave along with twomoles of lithium. The autoclave is then pressurized to one atmospherewith nitrogen and stirred for three hours at 15 C. The contents are thendischarged and a good yield of bis(dimethylcyclo pentadiene) nickel isseparated from the reaction product by means of chromatography.

Example 11 One mole of bis(methylcyclopentadienyl) cobalt dissolved insec-butyl alcohol is charged to an evacuated autoclave along with threemoles of potassium. The autoclave is pressurized to 75 atmospheres withargon. The mixture is then stirred for four hours at 20 C. whereupon thevessel is discharged. A good yield of methylcyclopentadienyl cobaltmethylcyclopentadiene is recovered by distilling the reaction productunder reduced pressure.

Example 12 Two moles of bis(cyclopentadienyl) cobalt dissolved inethylether is charged to an autoclave which is pressurized to oneatmosphere with hydrogen. One-tenth mole of platinum catalyst is addedto the autoclave and stirring of the reaction mixture is commenced. Thepressure in the autoclave is maintained at one atmosphere by feeding inhydrogen as the reaction progresses. When one mole of hydrogen has beenfed to the autoclave, stirring is ceased and the autoclave isdischarged. The product is filtered and the filtrate is reduced todryness by heating under reduced pressure. The residues are sublimed togive a good yield of cyclopentadienyl cobalt cyclopentadiene.

Example 13 One mole of bis(methylcyclopentadienyl) nickel dissolved inbenzene is charged to an autoclave pressurized to five atmospheres withhydrogen. Copper chromite is then added to the autoclave in an amountequal to percent by weight of the bis(methylcyclopentadienyl) nickelreactant. The reaction mixture is stirred at 50 C. until a pressure dropis noted which is equivalent to one mole of hydrogen being consumed inthe reaction. Agitation is then stopped and the reaction vessel isdischarged. A good yield of bis(methylcyclopentadienyl) nickel isobtained by distillation from the reaction product.

Example 14 One mole of bis (phenylcyclopentadienyl) rhodium dissolved indiethylene glycol dimethylether is charged to an autoclave pressurizedwith hydrogen to one atmosphere. Finely divided palladium catalyst isadded which is equal to two weight percent of the his(phenylcyclopentadienyl) rhodium. The reaction mixture is stirred at 40C. Pressure in the reaction vessel is maintained constant at oneatmosphere by slowly adding hydrogen to the system as hydrogen isconsumed in the reaction. When /2 mole of hydrogen has been added to thesystem in maintaining the pressure at one atmosphere, stirring is ceasedand the reaction vessel is discharged. A good yield ofphenylcyclopentadienyl rhodium phenylcyclopentadiene is obtained fromthe reaction product by means of chromatography.

The compounds made according to the process are useful antiknocks whenadded to a petroleum hydrocarbon. They may be used as primary antiknocksin which they are the major antiknock component in the fuel or also assupplemental antiknocks. When used as supplemental antiknocks, they arepresent as the minor antiknock component in the fuel in addition to aprimary antiknock such as tetralkyllead compound. Typical alkylleadcompounds are tetraethyllead, tetrabutyllead, tetramethyllead andvarious mixed lead alkyls such as dimethyldiethyllead,diethyldibutyllead and the like. When used as either a supplemental orprimary antiknock the compounds produced by the process may be presentin the gasoline in combination with typical scavengers such as ethylenedichloride, ethylene dibromide, tricresylphosphate and the like.

The compounds produced by my process are further useful in many metalplating applications. In order to effect metal plating using thecompounds produced by 10 my process, they are decomposed in an evacuatedspace containing the object to be plated. On decomposition, they laydown a film of metal on the object. The gaseous plating may be carriedout in the presence of an inert gas so as to prevent oxidation of theplating metal or the object to be plated during the plating operation.

The gaseous plating technique described above finds wide application informing coatings which are not only decorative but also protect theunderlying substrate material. When the metal laid down is a conductorsuch as nickel this technique enables the preparation of plated circuitswhich find 'wide application in the electrical arts.

Deposition of metal on a glass cloth illustrates the applied process. Aglass cloth band weighing one gram is dried for one hour in an oven at150 C. -It is then placed in a tube which is devoid of air and there isadded to the tube 0.5 gram of bis(cyclopentadiene) nickel. The tube isheated at 400 C. for one hour after which time it is cooled and opened.The cloth has a uniform metallic grey appearance and exhibits a gain inweight of about 0.02 gram. The cloth has greatly decreased resistivityand each individual fiber proves to be a conductor. An application ofcurrent to the cloth causes an increase in its temperature. Thus aconducting cloth is prepared which can be used to reduce staticelectricity, for decorative purposes, for thermal insulation byreflection or as a heating element.

Having fully described my novel process, I desire to be limited onlywithin the scope of the appended claims.

I claim:

1. Process for preparing a cyclopentadiene metal compound selected fromthe class consisting of cyclopentadienyl cobalt cyclopentadienes,cyclopentadienyl iridium cyclopentadienes, cyclopentadienyl rhodiumcyclopentadienes, and bis(cyclopentadiene) nickels wherein thecyclopentadiene and cyclopentadienyl groups are hydrocarbon groupshaving from 5 to about 13 carbon atoms; said process comprising reactingthe corresponding neutral bis(cyclopentadienyl) metal compound at atemperature within the range of about 20 C. to about C. with a reducingagent selected from the class consisting of A. alkali metals, alkalimetal amalgams and simple and complex alkali metal hydrides, whereinsaid process is conducted in the presence of a hydrolytic solvent and B.hydrogen, in the presence of a catalytic quantity of a catalyst selectedfrom the class consisting of Raney nickel, platinum, palladium andcopper chromite, wherein said process is conducted in the presence of asolvent selected from the class consisting of hydrolytic andnon-hydrolytic solvents.

2. The process of claim 1 wherein the reducing agent is an alkali metalamalgam and a hydrolytic reaction solvent is employed.

3. The process of claim 1 wherein the reducing agent is an alkali metalhydride selected from the group consisting of complex alkali metalhydrides and simple a1- kali metal hydridcs and a hydrolytic reactionsolvent is employed.

4. The method of claim 1 wherein the reducing agent is an alkali metaland -a hydrolytic reaction solvent is employed.

5. The process of claim 1 wherein the reducing agent is hydrogen.

6. The process of claim 5 wherein the reduction reaction is carried outin the presence of a hydrogenation catalyst.

7. The process of claim 1 wherein the bis(cyclopentadienyl) metalcompound is selected from the group consisting of cobalt, rhodium andiridium and the product produced is a cyclopentadienyl metalcyclopentadiene compound in lWhlCh the metal is selected from the groupconsisting of cobalt, rhodium and iridium.

8. The process of claim 1 wherein the bis(cyclopentadienyl) metalcompound is a bis(cyclopentadienyl) nickel compound and the productproduced is a bis(cyclopentadiene) nickel compound.

9. The process of claim 2 wherein the alkali metal amalgam containsbetween about 2 to about 5 percent by weight of alkali metal.

10. Process comprising reacting bis(eyclopentadienyl) nickel with analkali metal amalgam containing from about two to about 5 percent byweight of alkali metal in the presence of a hydrolytic solvent at atemperature within the range of about 20 C. to about 100 C. and under anatmosphere of an inert gas to yield bis(cyclopentadiene) nickel.

11. Process comprising reacting bis(cyclopentadienyl) cobalt with analkali metal amalgam containing from about two to about 5 percent byweight of alkali metal in the presence of a hydrolytic reaction solventat a temperature within the range of about --20 C. to about 100 C. andunder an atmosphere of an inert gas to yield cyclopentadienyl cobaltcyclopentadiene.

12. Process comprising reacting bis(cyclopentadieuyl) nickel withhydrogen in the presence of absolute ethanol and a catalytic quantity ofRaney nickel at a temperature within the range of about 0 C. to about C.to yield bis cyclopentadiene) nickel.

13. Process comprising reacting bis(cyclopentadienyl) nickel with sodiumborohydride in the presence of a hydrolytic solvent at a temperaturewithin the range of about 0 C. to about 100 C. and under an atmosphereof an inert gas to yield bis(cyclopentadiene) nickel.

References Cited in the file of this patent UNITED STATES PATENTS HavenOct. 22, 1957 OTHER REFERENCES

1. PROCESS FOR PREPARING A CYCLOPENTADIENE METAL COMPOUND SELECTED FROMTHE CLASS CONSISTING OF CYCLOPENTADIENYL COBALT CYCLOPENTADIENES,CYCLOPENTADIENYL IRIDIUM CYCLOPENTADIENES, CYCLOPENTADIENYL RHODIUMCYCLOPENTADIENES, AND BIS(CYCLOPENTADIENE) NICKELS WHEREIN THECYCLOPENTADIENE AND CYCLOPENTADIENYL GROUPS ARE HYDROCARBON GROUPSHAVING FROM 5 TO ABOUT 13 CARBON ATOMS; SAID PROCESS COMPRISING REACTINGTHE CORRESPONDING NEUTRAL BIS(CYCLOPENTADIENYL) METAL COMPOUND AT ATEMPERATURE WITHIN THE RANGE OF ABOUT -20*C. TO ABOUT 100*C. WITH AREDUCING AGENT SELECTED FROM THE CLASS CONSISTING OF A. ALKALI METALS,ALKALI METAL AMALGAMS AND SIMPLE AND COMPLEX ALKALI METAL HYDRIDES,WHEREIN SAID PROCESS IS CONDUCTED IN THE PRESENCE OF A HYDROLYTICSOLVENT AND B. HYDROGEN, IN THE PRESENCE OF A CATALYTIC QUANTITY OF ACATALYST SELECTED FROM THE CLASS CONSISTING OF RANEY NICKEL, PLATINUM,PALLADIUM AND COPPER CHROMITE, WHERIN SAID PROCESS IS CONDUCTED IN THEPRESENCE OF A SOLVENT SELECTED FROM THE CLASS CONSISTING OF HYDROLYTICAND NON-HYDROLYTIC SLVENTS.